In the field of agriculture and horticulture, it is well known to use spray oils in the control plant pests such as harmful insects, fungi, and microorganisms such as bacteria and viruses. The base for such spray oils are generally made of naturally occurring oils such as refined petroleum products, e.g., paraffinic oils, or oils extracted from plants, vegetables or animals.
Spray oils are often formulated as an oil-in-water (O/W) emulsion which is periodically applied directly to plants. An emulsion is a dispersed system containing at least two normally immiscible phases, one being dispersed as droplets in the other. Emulsions are thermodynamically unstable due to excess free energy associated with the surface of the dispersed droplets such that the particles tend to flocculate (clumping together of dispersed droplets or particles) and subsequently coalesce (fusing together of agglomerates into a larger drop or droplets) to decrease the surface energy. If these droplets fuse, the emulsion will “break”, i.e. the phases will separate, destroying the emulsion and making it difficult to prepare formulations that have a suitable shelf-life for storage. To prevent or slow breaking of an emulsion, an emulsifying agent is typically added. The type and concentration of a particular emulsifying agent will depend, inter alia, on the emulsion phase components and the desired result.
Spray oils are often used as a carrier for traditional synthetic chemical pesticides and for enhancing the activity of such pesticides. Alternatively, certain spray oils can be used alone as a bona fide pest control agent, in which case the oil component itself is the active ingredient. Spray oil alone is thought to act by coating the pests to induce a potential variety of effects, including suffocation of insects, modification of insect feeding and egg laying behavior, destruction of fungi cell walls, removal of humidity and interference with physical interactions of fungi or viruses with the host plant.
For a number of reasons, it is preferable to use spray oils without added chemical pesticides. For example, as compared with chemical pesticides, spray oils are generally considered to be safer for humans, are less harmful to beneficial insects such as bees, and are more quickly degraded. In addition, the cost of effort of manufacturing chemical pesticides is avoided, while spray oils can be simply made out of inexpensive fractions of petroleum oil. The main limitation of spray oils is their potential to cause plant injury (phytotoxicity) in some situations, as with certain sensitive plants or plants under drought stress.
The use of spray oil alone has been especially useful in effectively controlling a variety of pests in tree crops, such as apple and orange trees, grapes, vegetables, and flowering and ornamental plants. Examples of such commercially available spray oils include Stylet-Oil (JMS Flower Farms Inc., Vero Beach, Calif.) and PureSpray 10E (Petro-Canada, Calgary, Alberta), both of which contain paraffin oil, also known as mineral oil, as the active ingredient.
A particularly desirous use of spray oil alone is in the control of turfgrass pests. Turfgrass generally includes any maintained grass surface, such as lawns and golf courses. Turfgrass has been traditionally treated with synthetic chemical compounds to control pests, resulting is high maintenance costs and harmful effects to humans and the environment.
Although several non-petroleum spray oils have been disclosed as having use in treating turfgrass, such spray oils have not found widespread commercial use. For example, US patent application publication no. 2003/0198686 to Keen discloses the use of a spray oil composed of a combination of fish oil and plant oil to control turfgrass pests. However, fish oils tend to be phytotoxic due to alcohol and acid products formed by ester hydrolysis and have an unpleasant smell. US patent application publication no. 2003/0194454 to Bessette discloses the use of rosemary oil and wintergreen oil, alone or in combination, in controlling turfgrass pests; however, such non-petroleum oils tend to become rancid upon prolonged exposure to sunlight.
To Applicant's knowledge, there is no petroleum-based spray oil indicated for use on turfgrass. Although Stylet-Oil, provided as a concentrate of 97.1% v/v paraffin oil and 2.9% v/v non-ionic emulsifier, is indicated for use against stripe rust disease on grass grown for seed when applied at an oil dosage of 0.2-0.4 gal/acre, it is well established that turfgrass differs significantly from grass grown for seed in several respects. For example, the major diseases that affect grass grown for seed and turfgrass are not coterminous. In particular, as outlined in the Online Guide to Plant Disease Control of Oregon State University Extension (http://plant-disease.ippc.orst.edu/) and in the hardcopy version, “The 2004 PNW Plant Disease Management Handbook”, the diseases of prime concern in the production of grass grown for seed include Rusts, Smuts, Molds, Silvertop, Barley Yellow Dwarf, Blind Seed, Ergot, Powdery Mildew, while the diseases of prime concern in turf management include Anthracnose, Dollar Spot, Brown Patch, Grey Snow Mold and Pink Snow Mold. Further, for the few diseases that are in common, the chemical treatment regimes can be different. For example, although Powdery Mildew is not a major problem in turfgrass, when necessary, treatment with azoxystrobine fungicide is recommended at a dosage of 4.1-8.7 oz of solid azostrobine per acre, compared with 1.65-4.05 oz of solid azoxysrtobine per acre for grass grown for seed. The differences between grass grown for seed and turfgrass may be due to physiological and physical differences imposed by different growing conditions and environments, the greater degree of stress imposed on turfgrass due to injuries caused by traffic and repeated mowing of turfgrass, and the removal of pest control agents when the turfgrass in mowed.
In view of the foregoing, there is a need in the art for an improved spray oil composition for control of pests of turfgrass.